1. Field of the Invention
The present invention relates to an artificial photosynthesis module that decomposes an electrolytic aqueous solution into hydrogen and oxygen with light, and particularly, to an artificial photosynthesis module having electrodes in which a photocatalyst layer of an electrode portion is tilted with respect to a direction in which an electrolytic aqueous solution flows.
2. Description of the Related Art
Hydrogen generating devices that electrolyze water to generate hydrogen, with the electricity generated using fossil fuels, have been suggested in the past. Meanwhile, clean energy for not depending on fossil fuels and fossil resources is required from viewpoints of the current environmental destruction on a global basis, permanent energy problems, and the like.
Artificial photosynthesis has been learned from plant photosynthesis and is attracting much attention as a method of obtaining energy and resources with inexhaustible solar light, water, and carbon dioxide gas, without depending on fossil resources.
Devices that decompose an electrolytic aqueous solution to generate oxygen and hydrogen have been suggested in the past as one of the forms using solar light energy that is renewable energy.
For example, JP2004-256378A describes a method for producing oxygen and hydrogen from water in which an electrode, which oxidizes a reductant of the redox medium to change the reductant into an oxidant of the redox medium, is installed in an aqueous solution of a photocatalysis tank including a photocatalyst and the oxidant of the redox medium, and the reductant of the generated redox medium is electrolyzed, and oxidized to change the reductant into the oxidant of the redox medium. An electrode that oxidizes the reductant of the redox medium to change the reductant into the oxidant of the redox medium includes a comb-type electrode.
A carbon dioxide reduction device of JP2013-253269A includes a photoelectric conversion layer having a light-receiving face and a back surface, an electrolytic solution tank, first and second electrolyzing electrodes provided with the electrolytic solution being interposed therebetween in the electrolytic solution tank, and a CO2 supply unit that supplies carbon dioxide into the electrolytic solution tank. The photoelectric conversion layer and the first and second electrolyzing electrodes are connected together such that a photoelectromotive force of the photoelectric conversion layer is output to the first and second electrolyzing electrodes. The first electrolyzing electrode has a carbon dioxide reducing catalyst. The second electrolyzing electrode has an oxygen generating catalyst. The first and second electrolyzing electrodes are provided such that air bubbles are movable between the first and second electrolyzing electrodes. Additionally, the first and second electrolyzing electrodes have a comb-type structure having a trunk part and a plurality of branch parts extending from the trunk part, respectively. A branch part of the first electrolyzing electrode is disposed between two branch parts of the second electrolyzing electrode. A branch part of the second electrolyzing electrode is disposed between two branch parts of the first electrolyzing electrode.
In addition to these, a hydrogen-oxygen gas generating electrode is suggested in JP2005-171383A as a device that decomposes an electrolytic aqueous solution to produce oxygen and hydrogen. A hydrogen-oxygen gas generating electrode of JP2005-171383A includes an anode group consisting of a plurality of anode plates that are separated from each other and are lined up in parallel, and a cathode group consisting of a plurality of cathode plates that face the plurality of anode plates, respectively. A gap that introduces water is secured between the anode group and the cathode group. A pair of anode segments is formed by folding back an anode plate in a substantial U-shape, a pair of cathode segment is formed by folding back a cathode plate in a substantial U-shape type, and the pair of anode segments and the pair of cathode segments are alternately inserted therebetween. In JP2005-171383A, a power source is connected to the anode group and the cathode group, respectively, and the water introduced into the gap is electrolyzed by applying positive and negative electric charges to the anode group and the cathode group, respectively.
WO2010/140353A describes photoelectrochemical cell including a first electrode that includes a conductive substrate and an optical semiconductor layer disposed on the conductive substrate, a second electrode that is disposed to face a face of the first electrode on the conductive substrate side and is electrically connected to the conductive substrate, an electrolytic solution that is in contact with a surface of the optical semiconductor layer and a surface of the second electrode and includes water, a container that accommodates the first electrode, the second electrode, and the electrolytic solution, a supply port for supplying water to the inside of the container, and an ion passage part that allows ions to move between the electrolytic solution in a first region on the surface side of the optical semiconductor layer and the electrolytic solution in a second region of the first electrode opposite to the first region. As the optical semiconductor layer is irradiated with light, the photoelectrochemical cell decomposes the water in the electrolytic solution to generate hydrogen.
JP2006-213932A describes an electrolytic bath having a membrane-electrode structure in which membrane-like electrodes for generating electrolyzed water are formed on both surfaces of an ion-permeable membrane. In JP2006-213932A, electrolyzation is performed by supplying pure water to a cathode side and an anode side and applying a voltage to between the electrodes for generating electrolyzed water, thereby generating hydrogen from the cathode side and generating oxygen from the anode side.
Additionally, JP2006-213932A describes that the electrodes for generating electrolyzed water have a mesh shape or a comb shape. JP2006-213932A describes that, in a case where the electrodes for generating electrolyzed water are formed in the comb shape, the electrodes may be provided at positions that overlap each other.